This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Animals were sampled from May 2009 [unreadable]September 2009 as follow-up from viral challenge in March 2009. Samples were used to monitor immune response, plasma viral loads (PVL). In September 2009, ten of the original 16 animals were treated four times with anti-CD8 antibody. Prior to the anti-CD8 treatment, all ten animals had undetectable PVL (four animals never exhibited detectable viral loads, six animals had positive viral loads after challenge but were undetectable at least 21 days prior to treatment). Blood samples were collected through November 2009 to monitor CD8 levels, immune response and plasma viral loads. After treatment, all animals showed significant drops in CD8 levels followed by a slow recovery of CD8 cells. The PVL of five of the treated animals remained below detectable limits after treatment. Five of the animals exhibited a resurgence of plasma viral loads after anti-CD8 treatment (all had previously exhibited detectable viral loads after challenge). Within 30 days after anti-CD8 treatment, the PVL of these five animals returned to below detectable limits.